1. Field of the Invention
The present invention relates to a light emitting element using electroluminescence. The present invention also relates to a light emitting device and an electronic device each including the light emitting element.
2. Description of the Related Art
In recent years, light emitting elements using electroluminescence have been actively researched and developed. In a basic structure of the light emitting element, a light emitting substance is interposed between a pair of electrodes. Light emission from the light emitting substance can be obtained by voltage application between the electrodes.
Such a light emitting element is of a self-light emitting type; therefore, it has advantages over a liquid crystal display in wide viewing angle, excellent visibility, high response speed, and capability of reduction in thickness and weight.
Light emitting elements can be divided into two groups: an organic light emitting element using an organic compound as a light emitting substance, and an inorganic light emitting element using an inorganic compound.
Note that these light emitting elements differ from each other in not only light emitting substance but also light emitting mechanism and characteristic.
Of them, the inorganic light emitting element has a double insulating structure which includes a light emitting layer 1503 interposed between insulating films (a first insulating film 1502 and a second insulating film 1504), between a pair of electrodes (a first electrode 1501 and a second electrode 1505), and provides light emission by application of an alternating voltage between both electrodes (the first electrode 1501 and the second electrode 1505) from respective power sources (a first power source 1506 and a second power source 1507), as shown in FIG. 15.
However, although the inorganic light emitting element has more excellent material reliability than the organic light emitting element, sufficient luminance and the like have not been obtained and various researches have been carried out (for example, see Reference 1: Japanese Published Patent Application No. 2001-250691).
Further, the inorganic light emitting element requires application of a voltage of several-hundred volts to the light emitting element due to its light emitting mechanism which provides light emission through collisional excitation of a light emitting center by electrons accelerated with high electric field. It is important to reduce its drive voltage in order to apply the inorganic light emitting element to a display panel or the like.